This application claims the benefit of Korean Patent Application No. 2002-6506, filed Feb. 5, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid electrophotographic image forming apparatus, and more particularly, to a liquid electrophotographic image forming apparatus using a developing agent in which a non-volatile ink carrier is used as a solvent.
2. Description of the Related Art
FIG. 1 is a cross-sectional view of a conventional liquid electrophotographic image forming apparatus. Referring to FIG. 1, the liquid electrophotographic image forming apparatus includes a photosensitive belt 14, a charger 15 charging the photosensitive belt 14, an eraser 17 erasing a residual charge remaining on the photosensitive belt 14, laser scanning units (LSUs) 16 projecting light onto the charged photosensitive belt 14 and forming a latent electrostatic image, developing units 30 developing the latent electrostatic image, a dryer 18 absorbing and vaporizing a liquid carrier from the photosensitive belt 14, and a transfer unit 20 transferring the developed latent electrostatic image onto paper 23.
The photosensitive belt 14 is circulated by a plurality of rollers including a driving roller 11 and passive rollers 12 and 13. The paper 23 is fed into the transfer unit 20 by rotation of a transfer roller 21 and a fixing roller 22, and the image is transferred onto the paper 23.
The LSU 16 scans data related to colors, such as yellow (Y), cyan (C), magenta (M), and black (K), onto the photosensitive belt 14, and each developing unit 30 supplies a developing solution of a corresponding one of the colors onto the photosensitive belt 14.
The developing unit 30 includes a developing solution supplier 32 supplying a developing solution onto the photosensitive belt 14 and a developing container 31 capturing the developing solution that drops from the photosensitive belt 14. The developing container 31 includes a developing roller 36, a brush roller 37 removing the developing solution that is stained on the developing roller 36, a squeeze roller 34 separating a liquid carrier that does not form images from the developing solution that is supplied onto the photosensitive belt 14, and a plate 35 capturing the liquid carrier that is squeezed out of the squeeze roller 34 into the developing container 31. A collector 39 collects the developing solution.
The developing unit 30 includes the developing roller 36 charged to a predetermined voltage and maintaining a developing gap with the photosensitive belt 14 so that the latent electrostatic images for each color such as Y, C, M, and K, are developed, an injector supplying the developing solution to the developing gap, and the squeeze roller 34 that is placed to apply pressure onto the photosensitive belt 14. The developing solution includes ink having a concentration where a toner, which s transferred onto the paper 23 to form a print image, is dispersed, and the liquid carrier having a low concentration to transfer the toner to a region where the latent electrostatic image of the photosensitive belt 14 is formed.
The liquid carrier used as a solvent and the ink having a developing material representing one of the colors, such as Y, C, M, and K, are supplied from an ink cartridge 38 to the developing solution supplier 32. Thus, the developing solution having a proper concentration, in which the liquid carrier is mixed with the ink, is stored in the developing container 31, and then is supplied to the developing solution supplier 32. The developing solution supplier 32 supplies the developing solution to the photosensitive belt 14.
Since the developing solution having a concentration of 2.5-3% is used in the conventional developing unit 30, the ink having a concentration of 10-30% that is supplied from the ink cartridge 38 is diluted with the liquid carrier having the low concentration and is supplied to the developing unit 30.
In order to supply the developing solution prepared in the developing supplier 32 to a developing nip formed between the developing roller 36 and the photosensitive belt 14, the ink is supplied between the developing roller 36 and the photosensitive belt 14 using the developing solution supplier 32. The developing solution having the low concentration forms the latent electrostatic image on the photosensitive belt 14, and then the photosensitive belt 14 passes the squeeze roller 34 to remove a surplus liquid carrier from the photosensitive belt 14. A residual carrier is absorbed into the dryer 18 and is heated, vaporized, captured and compressed by a condenser, and then removed from the photosensitive belt 14.
The toner having a high concentration and forming an image on the photosensitive belt 14 is transferred to the transfer roller 21 by heat, pressure, or electrostatic force, and part of the residual carrier is vaporized by heat and pressure that is applied to the fixing roller 22 so that the image is retransferred onto the paper 23, and is thus printed out.
The liquid carrier is used in the conventional image forming apparatus as a liquid developing agent to obtain a high quality image. However, since a flash point of the liquid carrier of the developing solution is less than 80xc2x0 C., when the developed image having the liquid carrier is fixed at a temperature of more than 110xc2x0 C., the liquid carrier is vaporized, and then the liquid carrier smells. Thus, in order to prevent the smell of the vaporized liquid carrier, a complex vapor capture system supplying and capturing vapor of the vaporized liquid carrier is required, a volume of the image forming apparatus increases, and a structure of the image forming apparatus becomes complicated. An additional cooler is also required for the condensation of the captured liquid carrier.
In addition, in the conventional liquid eletrophotographic forming apparatus, since the concentration of the liquid developing solution is 2-3% and is different from the concentration of 10-30% of the ink that is provided in the ink cartridge 38, a complex ink supply system and a concentration controlling apparatus are required to prepare the developing solution having the concentration of 2-3% by mixing the ink having the high concentration with the liquid carrier. Also, a squeeze process is required to remove the surplus liquid carrier remaining in the liquid developing agent having the low concentration.
To solve the above and other problems, it is an object of the present invention to provide an image forming apparatus, which is capable of preventing a smell caused by vapor of a carrier and also capable of quickly providing a high quality image.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided a liquid electrophotographic image forming apparatus. The apparatus includes a photosensitive body, a charge unit increasing a potential of the photosensitive body to a charge potential, an exposure unit projecting a beam onto the photosensitive body and forming a latent electrostatic image, a developing solution supply unit supplying the photosensitive body with a developing solution having a high concentration where a non-volatile carrier is used as a dispersion solvent, a developing unit to which the developing solution having the high concentration is supplied to form a developing film having the high concentration and to develop the latent electrostatic image, a transfer unit contacting the photosensitive body and moving the developed image from the photosensitive body to a recording medium, and a fixing unit fixing the transferred image on the recording medium at a temperature lower than a flash point of the non-volatile carrier.
Here, the non-volatile carrier includes perfluocarbons (compounds including fluorine (F) and carbon (C)), silicon oil, vegetable oil, and hydrocarbon and has a relative permittivity and a low surface tension, and the flash point of the non-volatile carrier is higher than 90 C.
According to an aspect of the present invention, the developing solution having the high concentration has a concentration 2-40%, a glass transition temperature (Tg) of more than 30xc2x0 C., and a melting point (Tm) that is not 20xc2x0 C. higher than the flash point of the non-volatile carrier.
According to another aspect of the present invention, the apparatus further includes a metering unit forming an ink film having the high concentration.
According to an embodiment of the present invention, using liquid ink (developing solution) where the non-volatile carrier is used as the dispersion solvent, a smell generating due to vapor of a carrier during a printing operation or from a printed matter can be prevented. A fixing energy is reduced by using the developing solution having the high concentration. A dryer or a condenser removing a carrier is not required. Also, a high quality image can be acquired without contamination of a non-image portion during a contacting and developing operation, and a squeeze process of removing a surplus carrier is not required.